Automate connections in 2 columns of nodes
Partial solution (adding reroutes to all unused inputs and replacing them) :



If you prefer to read or didn't understand this rushed video :

So you have a bunch of nodes and you want to add reroutes to their inputs


add any node (doesn't matter which one since you'll delete it later)
move it on the left of your bunch of nodes
select your bunch of nodes and the new lonely one which you set as the active one
press K (with Node Wrangler enabled) to connect the lonely node to the bunch of nodes.
select and group the entire node tree except for the new lonely node which stays outside
in the group, Shift + left-click drag on the group input links to add reroutes on them
Tab to get out of the group
Alt+G to ungroup it
delete the lonely node you added previously
reorder your reroutes properly if some are not in the right place
Shift+= to arrange them perfectly


Voilà. Now you can replace those reroutes by any node with Shift+S. And if you need them to have specific parameters, don't forget Right-click > "copy to selected" to apply your changes from the active node to all the selected ones.